Semiconductor image sensors are used for sensing light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as cameras, scanners, photocopiers, etc. These devices utilize an array of pixels in a substrate, including photodiodes and transistors that can absorb radiation projected toward the substrate and convert the sensed radiation into electrical signals.
A performance of an image sensor depends on, among other things, its quantum efficiency and optical crosstalk. The quantum efficiency of an image sensor indicates a number of electrons generated per number of incident photons in the image sensor. The optical crosstalk occurs when some photons incident upon a pixel are absorbed by another pixel.
Therefore, while existing semiconductor structures of image sensors and conventional methods of manufacturing image sensors have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.